Conventional dental handpieces are known, for example, from JP-2005-342403-A. FIG. 9 shows a dental handpiece disclosed in this publication, which includes a grip section 43 having a head section 42, to which a treatment tool 41 is detachably attached, and a motor casing (drive section) 50 detachably connected to the grip section 43. This dental handpiece is of a contra-angle type, wherein the casing of the grip section 44 includes a front casing portion 44F continuous to a rear casing portion 44R obliquely at an obtuse angle. In the rear casing portion 44R, a first rotary shaft 45 is rotatably supported, and in the front casing portion 44F, a cylindrical jacket 46 extending from the head section 42 is inserted toward the first rotary shaft 45 and fixed. The jacket 46 rotatably supports therein a second rotary shaft 47, which is operatively connected to the treatment tool 41 and linked to the first rotary shaft 45 via gears 48 and 49. A motor shaft 51 extends from the motor casing 50, and drivingly connected to the first rotary shaft 45. In this manner, the driving force of the motor in the motor casing 50 is transmitted by means of the first and second rotary shafts 45 and 47 to the head section 42, where the treatment tool 41 is driven.
In this type of dental handpiece, the jacket inserted into the front casing portion is fixed therein conventionally by means of a screw which is fastened into a screw hole provided through the peripheral surface of the front casing portion, as shown, for example, in FIG. 4 of JP-7-51136-B. However, as the handpiece is used, the screw is loosened, which causes the head section to shake. This impairs the operability of the handpiece and makes the treatment hard for the practitioner.
In addition, this type of dental handpiece enjoys excellent appearance due to the good design of its casing. However, the screw exposed on the peripheral surface of the casing impairs the appearance of the handpiece.